The present invention relates to ultrafine particles applied to selected carrier particles, a method for the production of the particle composite materials, and their use as fillers for polymers or as catalysts for cross-linkable polymers and as stabilizers in polymers.
When ultrafine particles are used in polymers, in particular in elastomers or thermoplastics, or in lubricating greases, the optimum distribution of the particles is very important in order to be able to exploit their potential as well as possible. This goal may only be implemented in exceptional cases through the introduction of mechanical energy.
Methods for producing ultrafine particles on ceramic and carbon-based carriers are known from the field of heterogeneous catalysis. As described in C. Prado-Burguete et al. in Journal of Catalysis 128 (1991) 397-404, for example, by impregnating carbon blacks with hexachloroplatinic acid and subsequent oxidation using oxygen and reduction using hydrogen, ultrafine platinum particles having 1 nm to 10 nm diameters may be obtained depending on the preparation and reaction conditions selected. Any prior activation of the carrier typically occurs here under a specific gas atmosphere at elevated temperatures.
A method for producing precipitated silicic acids, which may be used as fillers in elastomers, is described in U.S. Pat. No. 6,146,454. The precipitated silicic acids have a zinc content of 1 to 5 wt.-percent, are provided in spherical form, and are characterized by an array of further physical parameters. Spherical silica gels having mean diameters of more than 80 μm are used as the carrier materials. There are no further details in the patent about the location at which the zinc is located in these particles.
EP-A-475,046 describes a method for producing granulates made of zinc oxide and silicic acid, which are obtained through precipitation of zinc oxide and silicic acid. The granulates may be dispersed well in rubber mixtures.
A method for producing fillers containing zinc oxide is known from DE-A-25 44 218.